This invention relates to a composition comprising a transition metal component and a magnesium carboxylate support. More particularly this invention relates to a composition comprising a titanium component and a support comprising the reaction product of carbon dioxide and a hydrocarbyl magnesium compound.
It is well known that normally solid, high molecular weight, predominantly crystalline polymers of alpha-olefins such as ethylene, propylene, butene-1, etc. can be prepared using a catalyst comprising an organoaluminum compound and a transition metal compound. Among such catalysts, those wherein the transition metal compounds are supported on a catalytically inert material, such as a metal oxide support, have been found particularly advantageous in the polymerization of ethylene and copolymerization of ethylene-dominated mixtures of alpha-olefins. Typically, such catalysts exhibit higher activities, give higher polymer yields and make more efficient use of transition metal compounds than do catalysts containing unsupported transition metal compounds. Until recently, however, supported transition metal catalyst components have found little or no commercial use in the stereospecific polymerization of alpha-olefins of three or more carbon atoms. While commonly assigned Karayannis, U.S. Pat. No. 4,277,370, which is hereby incorporated by reference, discloses a new catalyst for the stereospecific polymerization of alpha-olefins of three or more carbon atoms comprising an organoaluminum compound and a component prepared from a halogen containing compound of titanium (IV), organic electron donor and a pretreatment product of components comprising magnesium alcoholate, etc., the catalyst resulting from this process, like most of the catalysts of this art, has the drawback that the particles are of different sizes and shapes, including particles of undesirably small dimension, e.g. fines. Catalyst fines are a particular problem since most supported catalyst components for vapor phase polymerization of C.sub.3 or higher olefins are routinely abraded to provide the catalysts higher activity. When irregularly shaped catalysts are polymerized under vapor phase conditions, the resulting polymerizates assume the shape of the catalyst particles. Further, the polymerizates have an extremely broad particle distribution including a relatively high concentration of very small particles. Such polymerizates are less than ideal for further processing. Accordingly, there is a need for relatively uniform supported catalyst components. In addition to the foregoing, there is always a need for new catalyst components, particularly those of higher activity or capable of simpler production.
In commonly assigned application Ser. No. 592,910 now U.S. Pat. No. 4,540,679 filed Mar. 23, 1984 there is described a method of forming magnesium hydrocarbyl carbonate supported transition metal components of improved morphology by reacting CO.sub.2 with a magnesium alcoholate suspension to form a magnesium hydrocarbyl carbonate and reacting said magnesium hydrocarbyl carbonate with a transition metal component. For example, the magnesium hydrocarbyl carbonate support can be formed by suspending magnesium ethoxide in an alcohol medium, adding carbon dioxide until the magnesium ethoxide dissolves forming magnesium ethyl carbonate and precipitating the magnesium ethyl carbonate reaction product from the solution as discrete spheres and/or oblong particles by treating with anti-solvent, such as an alkyl aluminum compound or transition metal compound. If the magnesium ethoxide is suspended in a liquid hydrocarbon or halohydrocarbon, (free of alcohol) the addition of carbon dioxide results in the breaking apart of the magnesium ethoxide particles and the magnesium reaction product does not dissolve. In either case the magnesium support is relatively uniform, contains a relatively low level of fines and can be processed into an effective catalyst for the polymerization of olefins, particularly C.sub.3 olefins without any need for ball milling.
The general object of this invention is to provide a new class of catalyst components or catalysts comprising a transition metal component and a magnesium support. Another object of this invention is to provide a new class of catalysts or catalyst components having a reduced level of fines. Other objects appear hereinafter.